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-rw-r--r--include/linux/sched/mm.h4
-rw-r--r--mm/khugepaged.c3
2 files changed, 7 insertions, 0 deletions
diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index a3fda9f024c3..4a7944078cc3 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -54,6 +54,10 @@ static inline void mmdrop(struct mm_struct *mm)
* followed by taking the mmap_sem for writing before modifying the
* vmas or anything the coredump pretends not to change from under it.
*
+ * It also has to be called when mmgrab() is used in the context of
+ * the process, but then the mm_count refcount is transferred outside
+ * the context of the process to run down_write() on that pinned mm.
+ *
* NOTE: find_extend_vma() called from GUP context is the only place
* that can modify the "mm" (notably the vm_start/end) under mmap_sem
* for reading and outside the context of the process, so it is also
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index a335f7c1fac4..0f7419938008 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1004,6 +1004,9 @@ static void collapse_huge_page(struct mm_struct *mm,
* handled by the anon_vma lock + PG_lock.
*/
down_write(&mm->mmap_sem);
+ result = SCAN_ANY_PROCESS;
+ if (!mmget_still_valid(mm))
+ goto out;
result = hugepage_vma_revalidate(mm, address, &vma);
if (result)
goto out;